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AUTOMOTIVE FASTENERS

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Fasteners for every application

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Types of Mechanical Fasteners Bolts or cap screws Nuts Washers Studs Cotter pins Roll pins Snap rings

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And still more . . .

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Bolts The most common

threaded fastener Many variations Uses either a metric or

standard thread pitch measured in threads per inch or millimeters

The bolt size is its diameter.

Hex size is the wrench size. Length is measured from

hex to threaded end. Bolt grade markings are on

the top of the hex.

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Bolt Grades ( hardness)

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Naming Bolts

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Clamping Force

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Bolt Size The size of

the bolt is the diameter of the shank of the bolt.

Metrics in millimeters.

Standards in fractions of an inch.

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Bolt Length

The bolt length is the distance from the hex head to the end of the thread.

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Thread Pitch

Two general types of bolts used.

Standard fractional inch sizes.

Metric millimeter sizes.

Look at the top of the hex head to tell the difference.

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Thread Classification UNC-United

National Course UNF-United-

National Fine NPT-National Pipe

Thread Metric

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Bolt Designations First item is bolt

size which is the same as the bolt diameter.

Second item is the thread pitch.

Third is bolt length.

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Measuring Thread Pitch The pitch gauge

has teeth much like the threads. Put the gauge that fits into the threads and read the number on the gauge.

Standards in threads per inch.

Metrics in threads per millimeters.

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Hex Head Sizes

This is the size wrench that will be needed to install or remove a bolt.

Pay attention to metric or standard.

Torque to proper amount.

Metric

Standard

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Studs Studs look similar to a bolt but have no hex head for a wrench.

One end screws into an engine part and the other holds a different part on with a nut.

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Nuts

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Washers Washers help the

bolt head with support.

Washer can be lock washers to keep the bolt from working loose.

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. . . and more washers

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Cotter Pins

Cotter pins are used to secure nuts to shafts so they don’t come loose.

Often used with a castle nut.

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Snap Rings Snap rings are used

to secure bearings, gears, and linkages.

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Torque Wrenches Torque wrench

measure how much you are tightening a bolt.

Bolts can only take so much torque or they break off! That’s a bad thing.

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How Much Torque?

The amount to torque a bolt depends on two important items.

1 – The diameter of the bolt. (the fatter the stronger)

2 – The grade of the bolt. (the better the grade the more torque it can take)

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Bolt Torque Charts These are found

in repair manuals, service manuals and on computer data systems.

Torque Sequence

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Thread Lock

Compounds such as Locktite literally glue the threads so they don’t vibrate loose.

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Anti-Seize Compounds

Inhibits the threads from rusting up and totally jamming together.

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Screws

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Keys

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Shafts with splines

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Thread Repair Tools

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Taps & Dies

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Thread Inserts (helicoils)